Display system for plasma display panels

ABSTRACT

A display system for plasma display panels in which X- and Ydirection electrodes are disposed in opposing relation to each other with a discharge gas sealed space being defined therebetween; a dielectric layer is coated on at least the Ydirection electrodes; a lateral discharge between adjacent Xdirection electrodes is sequentially shifted; a vertical discharge is caused between the X- and Y-direction electrodes in accordance with the timing of the lateral discharge shifting and the timing of a write-in voltage selectively impressed to the Ydirection electrodes, the vertical discharge thus caused being stored as a wall voltage in the dielectric layer; and a sustain voltage is impressed between the X- and Y-direction electrodes after writing of one line or one picture frame to provide a display in accordance with the wall voltage pattern.

United States Patent 11 1 Urade et al. 1 1 Oct. 1, 1974 [541 DISPLAY SYSTEM FOR PLASMA DISPLAY 3,701,924 10/1972 Glaser 315/169 TV X PANELS 3,750,159 7/1973 Wojcik 340/324 M [75] Inventors: T oshinori Urade, Kobe; Tadatsugu Primary Examiner David L Trafton Hlmse Akashl both of Japan Attorney, Agent, or FirmStaas, Halsey & Gable [73] Assignee: Fujitsu Limited, Kawasaki, Japan 22 Filed: Dec. 29, 1972 1 ABgTRAflcT A display system for plasma display panels m which X- l l PP N05 319,933 and Y-direction electrodes are disposed in opposing relation to each other with a discharge gas sealed [30] Foreign Application priority Data space being defined therebetween; a dielectric layer is D c 31 ]a an 46485 coated on at least the Y-dlrectlon electrodes; a lateral e p discharge between adjacent X-direction electrodes is sequentially shifted; a vertical discharge is caused be- 340/324 78/73 542 2 22 tween the X- and Y-direction electrodes in accor- 581 Fie'ld 178/7 3 D dance with the timing of the lateral discharge shifting "5 R TV and the timing of a write-in voltage selectively impressed to the Y-direction electrodes, the vertical dis- [56] References Cited charge thus caused being stored as a wall voltage in the dielectric layer; and a sustain voltage is impressed UNITED STATES PATENTS between the X- and Y-direction electrodes after writ- 2,847,615 8/1958 Engelbart 315/846 ing of one line or one picture frame to provide a dislg; lf hp y play in accordance with the wall voltage pattern. O [150 I i 3.654507 4/1972 Caras et al. 315/169 TV X 5.C|a1ms, 11 Drawing Figures I! I f I I I I I I I, x 1 -I b l/ I l I) 3 I I I I 1 I, l "3 I y l X 1 1 /1 4 1 1 4 I 0| bl Cl 02 b2 02 a: G

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DISPLAY SYSTEM FOR PLASMA DISPLAY PANELS CROSS REFERENCE TO CO-PENDING APPLICATION Reference is made to co-pending US. application Ser. No. 319,940, filed Dec. 29, 1972, entitled, Display System for a Plasma Display Device, by Andoh, Shirouchi and I-Iirose, and assigned to the Assignee of this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a display system for plasma display panels for providing a display by utilizing the memory function of a wall voltage and the primary current effect due to electrons, ions and metastable atoms produced by discharge.

2. Description of the Prior Art In plasma display panels, a charge produced by discharge is stored in a dielectric layer coated on electrodes to generate a wall voltage and the wallvoltage provides a memory function. Further, ions, electrons and metastable atoms produced by discharge are scattered and self shift can be achieved by the primary current effect, which results in lower firing discharge voltages of adjacent cells. For this self shift, electrodes are periodically connected to usually three buses, electrodes are provided in the shifting direction which cross the electrodes in opposing relation thereto and a sustain voltage is impressed to the buses in a sequential order. Accordingly, written information is displayed while being shifted as is the case with an electric sign and it is displayed in a stationary condition by continuously impressing the sustain voltage to any one of the buses. However, in the case of such a stationary display, two electrodes are interposed between discharge spots in the shifting direction and the displayed image is indistinct. This can be avoided by narrowing the distance between the electrodes and decreasing their width, but this presents a problem in their manufacture.

Further, it has also been proposed to divide the discharge gas space into two equivalent layers, cause self shift in the one layer and produce a display in the other layer. However, this requires complicated construction and encounters a difficulty in the reduction of the pitch of one picture element.

SUMMARY OF THE INVENTION An object of this invention is'to provide a display system which employs a construction similar to those of usual plasma display panels and utilizes the shelf shift action but enables reduction of a picture element pitch.

Briefly stated, the display system for plasma display panels according to this invention includes a plurality of X-direction electrodes periodically connected with a plurality of buses and a plurality of Y-direction electrodes impressed with a display information input are disposed opposite to each other with a discharge gas space difined therebetween. A dielectric layer is coated on at least the Y-direction electrodes. A lateral discharge between adjacent ones of the X-direction electrodes is sequentially shifted, and a vertical discharge is caused between the X- and Y-direction electrodes in accordance with the timing of the lateral discharge shifting and the timing of the display information input impressed to the Y-direction electrodes. The vertical discharge is stored as a wall voltage in the dielectric layer, and a sustain voltage is impressed between all the X- and Y-direction electrodes after the writing operation to provide and maintain a display.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more fully understood by the following description and attached drawings, in which:

FIG. 1 is a cross-sectional view showing the principal part of an embodiment of this invention;

FIG. 2 shows electrode arrangements employed in the embodiment shown in FIG. 1;

FIG. 3 is a waveform diagram, for explaining the operation of the embodiment depicted in FIG. 1;

FIG. 4 is a block diagram showing a drive circuit employed in the embodiment of FIG. 1; and

FIGS. 5A to 5G show a series of waveform diagrams,

for explaining the operation of the circuit depicted in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows in section the principal part of one ex ample of a plasma display panel of this invention and FIG. 2 shows electrode arrangements employed therein. In FIG. 1, reference numerals 1a and 1b indicate insulating base plates as of glass, 2a and 2b indicatethe dielectric layers as of low-melting-point glass, 3x and 3y indicate the X- and Y- direction electrodes, and 4 indicates a discharge gas space having sealed therein a mixed gas composed of for example, neon and argon.

Reference characters A, B and C designate buses; electrode a1, b1, c1, a2, b2, of the X-direction 3x are connected to the buses A, B and C, respectively, in repeating groups of three; yl to y7 indicate electrodes of the Y-direction electrodes 3y, s indicates a starting electrode connected with a bus S; D1 to D7 indicate the drivers and CONT indicates-a control circuit including a decoder. With a starting signal, voltages VS and VA shown in FIG. 3 are impressed to the buses S and A as shown in FIG. 3 to cause a discharge between the electrodes s and al. This discharge is produced in a lateral direction, and hence will hereinafter be referred to as a lateral discharge. Then, upon impression of a voltage VB to the bus B, electrons, ions and metastable atoms produced by the aforementioned lateral discharge between the electrodes 5 and al are scattered and a lateral discharge is caused between the electrodes al and b1 by the primary current effect lowering the discharge voltage therebetween and by a wall voltage. In a similar manner, when a voltage VC is impressed to the bus C, a lateral discharge is produced between the electrodes b1 and cl. Namely, the lateral discharge is shifted from left to right in FIG. 2 by sequential impression of the voltages VA, VB and VC to the buses A, B and C. FIG. 3 shows that one continuous pulse during each pulse period is impressed for each of VS, VA, VB and VC but it is instead possible to impress a plurality of pulses within one pulse period.

For example, impressing a write-in voltage VY to the electrode y3 by driving the driver D3 with a signal from the control'circuit CONT at the timing of the generation of the lateral discharge between the electrodes 02 and b2, a discharge is caused between the electrodes 3. 3 and a2. This discharge is produced in a direction vertical to the lateral direction, and hence will hereinafter be referred to as a vertical discharge. The vertical discharge is produced mainly by the aforementioned selecting voltage VY and the primary current effect due to the lateral discharge between the electrodes a2 and b2. Further where the dielectric layer 20 is formed on the electrode b2, a wall charge stored in the dielectric layer 2a also serves to cause the vertical discharge. Thus, a wall charge is stored by the vertical discharge in the dielectric layer 2b overlying the electrode y3 opposed to the electrode b2 to provide a wall voltage. The wall charge stored in the dielectric layer 2a is neutralized when the lateral discharge is shifted but the wall charge stored in the dielectric layer 2b is neutralized only very slightly and also remains after shifting of the lateral discharge. Thus, desired information is sequentially written and stored as a wall charge, that is, a wall voltage in the dielectric layer 2b in accordance with the timing of shifting of the lateral discharge and that of impression of the selective write-in voltage VY to selected one(s) of the electrodes yl to y7.

Upon completion of writing of one line, voltages are simultaneously impressed to the buses A, B and C and voltages are also simultaneously impressed to the electrodes yl to y7. Namely, voltages are impressed as indicated by the display period in FIG. 3, providing a condition that a sustain voltage is impressed, in accordance with the usual plasma display panels. At this time, since the wall charge previously stored in the dielectric layer 2b is distributed in a pattern depending upon the pattern of the information written in, the discharge voltage in the area of the pattern is lowered, thus producing a discharge in that pattern. With the aforesaid writing, a discharge is caused between the electrodes y3 and a2 as indicated by a circle in FIG. 2. Namely, the display content uses as one picture element each of opposing intersections of the electrodes a1, bl, cl, and those yl to y7. This implies that the one picture element pitch is reduced, as compared with that of conventional plasma display panels in which the display content is formed with a picture element of every third electrode.

The above-described display system and its drive circuit will become clearer from FIG. 4. In FIG. 4, a display panel indicated by has X-direction electrodes a1, bl, c1, an, bn, and on including the starting electrode S, and Y-direction electrodes yl, y2, and yn extending in a direction perpendicular to the X direction electrodes, as described previously with regard to FIG. 2. The starting electrode S is connected through a driver 11s to a one-shot multivibrator 17 which is controlled with a reset output from a flip'flop circuit 16. The respectively. X-direction electrodes are connected to three drivers 11a, 11b and 11c through buses A, B and C. respectively. These drivers 11a, 11b

positive operating portions P of the respective preceding drivers 11c, 11a and 11b, and in common to a set output of the flip-flop circuit 16 through switching elements Sa, Sb and Sc which are closed by display command so that negative pulses are supplied to the buses only during the writing operation. Further, second input terminals of the AND gate circuits 12a, 12b and are connected to an oscillator 15 producing a pulse of about SOKHZ. The second input terminals of the OR gate circuits 13a, 13b and 13c'are connected to a set output of the flip-flop circuit 16 which provides display commands.

Further, the Y-direction electrodes are connected to a shift register 25, which affords information storage, through drivers 21a, 21b, and 2ln, AND gate circuits 22a, 22b, and 22n, OR gate circuits 23a, 23b, and 23n and AND gate circuits 24a, 24b, and 24n respectively. In the last stage of the shift register 25, a one-shot multivibrator 26 is provided, whose output is connected in parallel with second input terminals of the aforesaid AND gate circuits 24a, 24b, and 24m and, at the same time, is connected to the ring counter 14 through a delay circuit 27. Further, the second input terminals of the OR gate circuits 23a, 23b, and 23n are supplied with the set output from the flip-flop circuit 16, and the second input terminals of the AND gate circuits 22a, 22b, and 22n are supplied in reverse polarity with an output from the oscillator 15 through an inverter 18.

During operation, the oscillator 15 produces a pulse output such as shown in FIG. 5A and that a first stage I of the ring counter 14 is in its on stage. Under such conditions, when an interface circuit 20 including a decoder separates a write-in command from a data supplied thereto to provide an output therefrom, theoneshot multivibrator 17 is actuated by a reset output from the flip-flop circuit 16 to supply the starting electrode S with a voltage such as depicted in FIG. 513. At this time, since the AND gate circuit 12a is held open, the buses A and B are supplied with pulses of a voltage Vsl/2 which are opposite in polarity to each other as shown in FIG. 5C and 5D, but the voltage Vsl/2 is not of sufficient magnitude to cause a discharge between adjacent electrodes. However, the voltage Vs applied to the starting electrode S is selected at a value large enough to produce a discharge between the electrode 5 and the first X-direction electrode a1, so that a lateral discharge is caused between them. This lateral discharge acts to establish a primary current due to ions, metastable atoms and electrons between adjacent electrodes a1 and b1 thereby to reduce the discharge voltage therebetween to a value lower than the voltage Vsl, thus causing a lateral discharge between the electrodes al and b1.

During this operation, the interface circuit 20 supplies display information of one column to the shift register 25 through the AND gate circuit 19. Upon completion of this supply, the one-shot multivibrator 26 is triggered to provide an output such as depicted in FIG. 5F to open the AND gate circuits 24a, 24b, and 2411 to supply the Y-direction electrodes with the display information for one column of the display as is now stored in the shift register 25. Namely, on the first line of information, such as line 1 corresponding to X address line a the AND gate circuits 22a, 22b,

and 22n are opened, through which the pulse derived from the oscillator 15 is applied opposite in polarity to the drivers 21a, 21b, and 2111. As a result of this, a selected one of the Y-direction electrodes, for example, 2 is supplied with a voltage Vw such as shown in FIG. 5G which is of the same polarity as the voltage of the subsequent one of 5 the electrodes a1 and [11 causing a lateral discharge therebetween, that is, the electrode bl has a voltage applied thereto as shown in FIG. 5D, which is opposite in polarity to the voltage applied to the preceding electrode a1 as shown in FIG. 5C a vertical discharge P then is produced between the X- and Y- direction electrodes a1 and 2 by the aid of the primary current effect due to the lateral discharge between the electrodes a1 and b1. This vertical discharge P is stored in the form of a wall charge after the voltage to the Y- direction electrode is removed, as is the case with the 1 known plasma display panels.

The other output from the one-shot multivibrator 26 is delayed by the delay circuit 27 for a period of time necessary for the above-described first column write-in operation to be carried out and then is applied to the three-stage ring counter 14 to advance it one step. Thus, the second stage II of the ring counter 14 is put in its on state and the pulse supply to the bus A is cut off. At the same time, pulses of opposite polarities are applied to the buses B and C in such forms as depicted in FIGS. 5D and SE to shift the lateral discharge from between electrodes al and bl to occur now between the electrodes bl and cl. Under these conditions, if display information of a second column is introduced to each Y-direction electorde, it can be written at each intersecting point of the electrode bl with each Y- direction electrode.

Upon delivery of a display command from the interface circuit after the entirety of the' columns of information has been sequentially written in, in the manner described above, the flip-flop circuit 16 is reversed and its set output is applied to the OR gate circuits 13a, 13b and 130 for the X-direction electrodes and the OR gate circuits 23a, 23b, and 23:1 for the Y-direction electrodes. As a result of this, a sustain voltage is applied between all the X- and Y-direction electrodes to cause a vertical discharge and thereby produce a display at each area where the vertical discharge produced in the writing operation has been stored in the pattern of the wall charge. During this operation, the negative operating portions N of the drivers 11a, 11b and He on the side of the X-direction electrodes are made inoperative by the switching elements Sa, Sb and Sc. The waveforms shown in the right-hand portion in FIG. 5 illustrate such display mode. In this case, however, shifting of the lateral discharge is not limited specifically to the three-phase system employing three shift drivers but is possible with any desired multiphase system.

The foregoing embodiment employs a plasma display panel in which the dielectric layer 2a is formed on the electrodes a1, b1, cl, but since storage and display of the written information utilizes the wall charge stored in the dielectric layer 212 formed on the electrodes yl to y7, it is also possible to omit the dielectric layer 2a and produce the lateral discharge directly. In

this case, it is necessary to provide resistors, inductances and like impedances for lateral discharge current limitation.

In order to decrease interference of discharge in the direction of the X-direction electrodes, partition means can be provided along theY-direction electrodes on the 6 dielectric layer overlying the X-direction electrodes. The partition means can be formed with mechanical partition walls, resistive stripes or layers of a material of small coefficient of secondary electron emission.

With the display system of this invention, a vertical discharge is produced by selecting the Y-direction electrodes in accordance with the information written in, thereby to store a wall charge in the dielectric layer disposed on the Y-direction electrode. A sustain voltage than is impressed between the X- and Y-direction electrodes after completion of the writing of one or all of the columns to provide a display. The writing operation is achieved by self shift as has been described in the foregoing, so that an address circuit is simplified and each intersecting point of the electrodes is used as one picture element, enabling a high resolution display. Further, the number of buses for lateral discharge shifting can be increased and the timing of the lateral discharge shifting can be detected from the content of a counter or the like. If the timing for the lateral discharge shifting is made coincident with the write-in information by means of a control circuit, input information can be sequentially written from the beginning.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this invention.

We claim:

l. A method of operating a plasma display panel" comprising a plurality of X-direction electrodes and a plurality of Y-direction electrodes spaced from each other for receiving therebetween a discharge gas, and a dielectric layer disposed on the Y-direction electrodes, said method comprising the steps of:

a. sequentially applying a first voltage signal to adjacent pairs of electrodes of said first plurality to effect a lateral discharge between the adjacent pairs of electrodes and for shifting the discharge from one pair of electrodes to the next adjacent pair;

b. applying a write signal indicative of the display information to selected electrodes of said second plurality of sufficient magnitude to produce a vertical discharge between corresponding X- and Y- direction electrodes in accordance with the timing of the shifting of the lateral discharge and the application of the write signal to the Y-direction electrodes, the vertical discharge being stored as a wall voltage in the dielectric layer; and

c. applying sustain voltages between the X and Y- direction electrodes after the application of the write signals to provide a visual display in accordance with the pattern of stored wall voltages in the dielectric layer.

. A display system comprising: a plasma display panel comprising a first plurality of electrodes disposed in a first direction and a secdischarge from each such pair of electrodes to the next;

0. means for applying a write signal selectively to said second plurality of electrodes whereby a vertical discharge is established between electrodes of said first and second pluralities in accordance with the timing of the shifting of the lateral discharge and the application of the display information input signal, said vertical discharge being stored as a wall voltage in said dielectric layer; and

d. means for applying a sustain voltage between said first and second electrodes to provide a display of the pattern of the wall voltage stored in said dielectric layer associated with said second plurality of electrodes.

3. A display system as claimed in claim 2, wherein said second plurality of electrodes includes a start electrode, and there is further provided means for applying a start signal to said start electrode to initiate the lateral discharge.

4. A display system as claimed in claim 2, wherein there is included an interface means and a shift register, said interface means receiving a data signal and providing a display information output signal bearing the data content of the received signal to said shift register means, said shift register means storing the display information output signal and said write signal applying means responds to the stored display information signals for correspondingly and selectively applying said write signals to said second plurality of electrodes.

5. A display system as recited in claim 2 wherein said first plurality of electrodes includes successive groups thereof and there are further provided plural buses equal in number to the number of electrodes of each such group and connected in common to the corresponding electrodes of each such group, and means for controlling said lateral discharge voltage applying means to apply said lateral discharge voltage between a pair of said buses cyclically and in continuous succession to effect the sequential shifting of the lateral discharge from each such pair of electrodes to the next. k l l 

1. A method of operating a plasma display panel comprising a plurality of X-direction electrodes and a plurality of Ydirection electrodes spaced from each other for receiving therebetween a discharge gas, and a dielectric layer disposed on the Y-direction electrodes, said method comprising the steps of: a. sequentially applying a first voltage signal to adjacent pairs of electrodes of said first plurality to effect a lateral discharge between the adjacent pairs of electrodes and for shifting the discharge from one pair of electrodes to the next adjacent pair; b. applying a write signal indicative of the display information to selected electrodes of said second plurality of sufficient magnitude to produce a vertical discharge between corresponding X- and Y-direction electrodes in accordance with the timing of the shifting of the lateral discharge and the application of the write signal to the Y-direction electrodes, the vertical discharge being stored as a wall voltage in the dielectric layer; and c. applying sustain voltages between the X- and Y-direction electrodes after the application of the write signals to provide a visual display in accordance with the pattern of stored wall voltages in the dielectric layer.
 2. A display system comprising: a. a plasma display panel comprising a first plurality of electrodes disposed in a first direction and a second plurality of electrodes disposed in a second direction to traverse the first-mentioned direction and spaced from said first plurality of electrodes for receiving a discharge gas therebetween, and a dielectric layer disposed on said second plurality of electrodes; b. means for sequentially applying lateral discharge voltage between each adjacent pair of said first plurality of electrodes of sufficient magnitude to effect a lateral discharge between said each adjacent pair of electrodes and for sequentially shifting a lateral discharge from each such pair of electrodes to the next; c. means for applying a write signal selectively to said second plurality of electrodes whereby a vertical discharge is established between electrodes of said first and second pluralities in accordance with the timing of the shifting of the lateral discharge and the application of the display information input signal, said vertical discharge being stored as a wall voltage in said dielectric layer; and d. means for applying a sustain voltage between said first and second electrodes to provide a display of the pattern of the wall voltage stored in said dielectric layer associated with said second plurality of electrodes.
 3. A display system as claimed in claim 2, wherein said second plurality of electrodes includes a start electrode, and there is further provided means for applying a start signal to said start electrode to initiate the lateral discharge.
 4. A display system as claimed in claim 2, wherein there is included an interface means and a shift register, said interface means receiving a data signal And providing a display information output signal bearing the data content of the received signal to said shift register means, said shift register means storing the display information output signal and said write signal applying means responds to the stored display information signals for correspondingly and selectively applying said write signals to said second plurality of electrodes.
 5. A display system as recited in claim 2 wherein said first plurality of electrodes includes successive groups thereof and there are further provided plural buses equal in number to the number of electrodes of each such group and connected in common to the corresponding electrodes of each such group, and means for controlling said lateral discharge voltage applying means to apply said lateral discharge voltage between a pair of said buses cyclically and in continuous succession to effect the sequential shifting of the lateral discharge from each such pair of electrodes to the next. 